Differential pressure responsive device



DIFFERENTIAL PRESSURE RESPONSIVE DEVICE Original Filed Dec; 51, 1962 2Sheets-Sheet 2 60k6 4. MAM/mam H6 3 PAL p/x A Me 045:

' MEHR/A/ azam/v 40 INVENTORJ' ATTORNEY United StatesPatent ODIFFERENTIAL PRESSURE RESPONSIVE DEVICE George A. Mansfield, In, SouthBend, Ind., and Ralph P.

McCabe, Warren, and Mehrin Begian, Detroit, Mich., assiguors to HolleyCarburetor Company, Warren, Mich., a corporation of Michigan 1 Originalapplication Dec. 31, 1962, Ser, No. 248,412. Divided and thisapplication June 3, 1964, Ser. No.

6 Claims. c1. 60--39.09)

This application is a division of US. application Serial No. 248,412,filed on December 31, 1962, entitled Differential Pressure ResponsiveDevice.

This invention relates generally to means for detectmg fiameout andactuating the ignition system in a gas turbine engine, and morespecifically to a novel device that is responsive to a pressuredifferential caused by a par- .ticular rate of changeof pressure. 1

It is well known that a simple gas turbine engine flameout, such as mayoccur in flight due to such things as the entry of water into the aircompressor, may be corrected by re-igniting the engine. At the presenttime, this is done either manually by the pilot or bythe use of acontinuously operating ignition system. However, these methods are notcompletely satisfactory, since the former a is subject to human errorand the latter shortens the life device which may have a variety ofapplications involving a need for a specific type of response to a rateof change in pressure and which may be actuated by mechanical orhydraulic signals, as well as by the pneumatic actuation described inconnection with the preferred embodiment of theinvention disclosedherein.

. Still another object of the invention is to provide such a devicewhich is accurate and reliable, insuring repeatable and positivemaintenance-free operation.

Other objects, and advantages of the invention will become apparent asthe description proceeds, especially .when taken in conjunction 'withthe accompanying drawings which illustrate a preferred embodiment of theinvention and wherein: t r

FIGURE 1 is an elevational view in partial cross-sec.-

tion of a gas turbine engine having a device embodying the invention;

FIGURE 2 is an enlarged elevational view in partial cross-section of thedevice embodying the invention taken on the plane of line 2-2 of FIGURE1 and looking in the direction of the arrows;

, FIGURE 3 is a cross-sectional view taken on the plane of line 33 01";FIGURE 2 and looking in the direction of the arrows;

FIGURE 4 is an enlarged fragmentary cross-sectional view taken on theplane of line 4-4 of FIGURE 3 and looking in the direction of thearrows; 1 1

FIGURE 5 is a cross-sectional view taken on the plane of line 55 ofFIGURE 3 and looking in the direction of the arrows; r

FIGURE 6 is a cross-sectional view taken on the plane of line 6-6 ofFIGURE 2 and looking in'the direction of the arrows; and

provide such a FIGURE 7 is auenlarged fragmentary view of a portion ofthe FIGURE 6 structure.

Referring to the drawings in greater detail, FIGURES 1 and 2 illustratethe detectorassembly 10 is adapted to 3,232,651 Patented Feb. 1, 1966the ignition system 12 of a gas turbine engine 14, the assembly beingmounted on a flange 16 on the engine in any suitable manner, such as bya bracket 18 and bolts 20. A conduit 22 communicates either compressordischarge or burner pressure, as sensed by a pressure probe 24 locatedbetween the compressor or the burner and an inlet 26 to the detectorassembly 10. The detector assembly 10 includes a switch unit 28 whichactuates the ignition system 12 through a suitable wire lead 30 inresponse to an appropriate pressure signal.

As seen in FIGURE 3, the detector assembly 10 comprises a body 32 and acover 34, separated byseals 36 and held together by bolts 38. Lugs 40are provided on the body portion 32 for mounting the assembly 10 to thebracket 18. A diaphragm 42, diaphragm shield 44 and diaphragm retainer46 are confined between the body 32 and cover 34 so as to form chambers48 and 50 illustrated in FIGURE 3, the diaphragm 42 and shield 44surround the link 58 and are fixed for axial movement therewith by thesecond retainer 60 and the shield spacer 62. The link 58 has a centraltransverse opening 72 which communicates with the hold-in jets 63, eachof which contains a bleed hole 74 and serves as a restriction in thepassageway 70. If a single restriction were used in place of theplurality ofjets 68, its opening would haveto be so small that it couldmore easily become plugged by tiny particles, hence the series of jets68, each containing relatively larger openings, is employed. It is to benoted that the yoke stop 66 includes a slot across its face forming anopening 76 which communicates between the axial passageway and the upperchamber 50* when the link assembly 56 is in contact with the link stopscrew 54. The link 58 is preferably formed from the same material asbody 32 and cover 34 in order to eliminate differential expansionbetween these parts. The link 53 is caused to move in a true verticaldirection and prevented from sideward movement by a link guide 78(FIGURE 4), which is confined at its outer edge between the diaphragmretainer 46 and the cover 34-, and which is preferably formed from amaterial such as beryllium-copper in order to assure a minimalspringback" tendency.

A counterbalanced lever 80 is pivotally mounted in the transverseopening 72 of the link 58. Bearings 82 fitted into a hole through thelever 8t allow the lever 89 to rotate about a pivot pin 84 which isfixedly mounted between one wall of the body 32 and a plug 87 threadedlyattached to the other side of the body 32 (FIGURE 5). A seat 36 isprovided at the end 88 of the lever 80 so as to be positioned opposite asecond seat 90 provided in the manually adjustable plug 92 which isfixedly attached to the body 32. Confined between the two seats 86 and90 is an assembly 94 comprising a pair of cones 96, a pin 98 and aspring 100. The cones 96, the pointed ends of which fits into conicaldepressions in the two seats 86 and 90, are slidably mounted on the endsof the pin 98 and are urged apart by the spring 100. The function ofthis assembly 94 will be described later.

The link assembly 56 further includes near its lower end second andthird transverse openings 162 and 164 perpendicular to one another and asecond axial passageway 1tl6 having a detent spring 108 containedtherein. A trunnion link .110 is rotatably and loosely confined in thesecond transverse opening 102. The trunnion link 110 includes a hole 112through its body perpendicular to its axis. The end 114 of a secondlever 116 extends into the third transverse opening 104 in the link 58and is press fitted into the hole 112 through the trunnion link 110 formovement therewith.

The other end 118 of the lever 116 is slotted inwardly at 120 to atransverse hole 122 which may have a serrated wall surface for a morepositive non-slipping connection with a shaft 124 having knurled ends126 and 128 (FIGURE A screw 130 drawing the split portions together maybe employed to assure a good grip of the lever 116 on the knurled end126 of the shaft 124.

As illustrated in FIGURE 5, the shaft 124 extends through an internalwall 132 in the main body 32 forming a third chamber 134 therein. Theshaft 124 is free to revolve in bearings 136, a bearing spacer 138 andbushing 140 fixedly located in the wall 132. A seal 142 confined by thebushing 140 prevents any dirt particles in the accumulator chamber 48from entering the third chamber 134. An adjustment lever 144 in thethird chamber 134 is attached at its one end to the knurled end 128 ofthe shaft 124 and fastened rigidly thereto by means of a split section146 and screw 148, as better seen in FIGURE 6. Axial adjustment of theshaft 124 and lateral position of the lever 144 is maintained by a screw150 threaded in the main body 32. Assembly of the shaft 124 and the twolevers 116 and 144 may be facilitated by means of an access openingcovered by plug 152.

The other end of the adjusement lever 144 is held in a pivotalrelationship with a contact lever 154 by means of a pin 156. While thepin 156 provides a pivotal relationship between the levers 144 and 154,it is connected only to the two levers 144 and 154 and therefore permitstheir combined vertical movement. The other end of the contact lever 154also pivots about a second pin 158 but is restrained from verticalmovement by virtue of the second pin 158 being fixedly attached to acontact retainer cup 160 (FIGURE 5 The lateral location of the retainercup 160 may be adjusted by shims 162 and spacer 164 confined in thethird chamber 134 by a gasket 166 and cover plate 168 fastened to thebody 32 in any suitable manner, such as by bolts 170.

Referring now to FIGURES 6 and 7, the retainer cup 160 is seen toinclude a punched-out portion 172 having two holes 174 therethrough inalignment with two holes 176 through the contact lever 154. Fastenedthrough these four holes 174 and 176 are two pairs of contacts 178 and180 facing and normally spaced apart from each other. However, the pairsof contacts 178 and 180 will at times contact each other by virtue ofthe above mentioned vertical movement of the levers 144 and 154 andtheir common pivot pin 156.

Leading from the contacts 178 and 180 are two pairs of wire leads 182and 184 which are attached in some suitable manner to the hermeticallysealed electrical connector 28. The latter is connected to the engineignition system 12 by the wire lead 30 shown in FIGURE 1.

A servo valve assembly 186 is incorporated in the system (FIGURE 3)between the upper and lower chambers 50 and 48 for a purpose which willbe described later. The cover 34 contains a drilled hole 188 into whicha servo spring seat 190 is pressed. A passageway 192 communicatesbetween the upper chamber 50 and the drilled hole 188. A second drilledhole 194 in the main body 32 is aligned with the upper drilled hole 188and contains a valve seat 196 at the bottom thereof. A servo valve 198is normally biased against the valve seat 196 by a spring 200 which isconfined between the servo valve 198 and the servo spring seat 190. Thecounterbalanced lever 80 contains a set screw 202 located directlybeneath the servo valve 198. The set screw 202 is adjustable through anormally plugged hole 204 in the main body 32. A needle 206 extendsupwardly from the set screw 202 so as to be able at times to lift theservo valve 198 off the valve seat,

196, compressing the spring 200. The unseating of valve 198 would occuronly after a predetermined counter clockwise movement by thecounterbalanced lever about the pivot pin 84.

Operation While the above described device may have a variety ofapplications, its operation will now be discussed in conjunction withthe ignition system of a gas turbine engine.

It may be helpful for a better overall understanding of the invention tofirst describe its operation generally. Because of its restrictedcommunication with chamber 50, chamber 48 serves as a type ofaccumulator and maintains a pressure that is substantially equal tosteady state compressor discharge or burner pressure, depending uponwhere the pressure probe 24 is located.

In addition to the chamber 48 serving as an accumulator, it also housesa novel toggle assembly 94 which serves to maintain the link assembly 56against the bottom stop 208 so long as the pressure in chamber 50 doesnot drop below the pressure in chamber 48 a predetermined amount. Thatis, the toggle assembly 94 serves to hold the link assembly 56 againststop 208, regardless of the rate of change in pressure at probe 24 andregardless of the magnitude of the pressure in either chamber, so longas the critical pressure differential between these chambers is notexceeded. However, whenever the rate of decrease of pressure in chamber50 is such that the previous differential between the two chambersexceeds a particular critical value, the toggle assembly 94, having thesnapaction effect of a negative spring modulus, will acceleate the linkassembly 56 upwardly. This novel acceleration characteristic will beexplained more fully in the discussion which follows later.

This upward movement of the link assembly 56 effects the opening of thecontacts 178 and so that, in the case of a gas turbine engineapplication, the current flow from the alternator of the ignition system12 would be diverted from the switch 28 to the igniter plugs of theengine for the reignition thereof. While ignition systems heretoforeused mere continuously operating, the invention causes the igniting ofthe plugs to continue only until the engine has ignited and the pressurein chamber 50 once again builds up to the extent that the pressuredifferential between chambers 48 and 50 is below the critical value, atwhich time the novel toggle assembly 94 moves the link assembly 56downwardly until the latter abuts once again against the bottom stop208. This, of course, recloses the contacts 178 and 180.

The complete operation will now be explained in detail. In thisconnection, it will be apparent that the accumulator pressure,hereinafter referred to as P in the lower chamber 48 would besubstantially equal to a compressor discharge or burner pressure atprobe 24, hereinafter referred to as P so long as the engine 14 isoperating normally. Under this condition, the link 58 would be seatedagainst the stop 208 at the bottom of the main body 32, the yoke stop 66at the top of the link assembly 56 would be positioned away from thelink stop screw 54 and the lever 116 would have been rotated downwardly,revolving the connector shaft 124. This, in turn, would have rotated theadjustment lever 144 and the attached contact lever 154 downwardly inthe third chamber 134 so as to close the pair of movable contacts 180against the other stationary pair of contacts 178 mounted on theextension 172 of the contact retainer cup 160, it being remembered thatclosing the contacts 178 and 180 blocks the flow of current to theigniter plugs. Furthermore, the link 58 would have pulled thecounter-balanced lever 80 downwardly about the pivot pin 84, therebyforming an angular relationship between the axis of the lever 80 and theaxis of the toggle assembly 94, for a purpose which will be describedlater.

In the above described condition of the device 10, the needle 206extending from the set screw 202, which is threadedly attachedtothecounter-balan ced lever 80; will have unseated the valve 198,asdescribed aboveu The function of the detent spring 108 locatedin thepassageway 106 near the'bottorri oil the link5'8 should now be noted.The system is designed so that once-the pairs of'contacts 1 '78 and180oorne into contact witheach other, the link 58 will be so'mepredeterminedtdistance, say .040 inch, from the bott-om stop 208. The:adjustment lever 144 in the third chamber 134" and the. associated lever11-6 in the second chamber 48-willf have reached the limit oftheindownward movement by. virtue of the contacts 180 having becomestoppedragains't the stationary contacts 178. Further" downwardmovement: of the link 58 will thuscausethe' detent spring-1- 108 tobecome compressed by the now stationary. trunnion link 110 at the endofthelever 1 16. It c'an'thusbe seen that the link assembly 56 wouldlikewise have to be" moved upwardly about .0'40 inch before; any upwardmovement of the trunnion link 1 and'the lever' 1'1'6 begins... This ispossible by virtue of theaclearance between the trunnion link 110 andthetransvcrsefopening 102 through'the link 58. This technique isemployed in order that the contacts 178 and 180 may he instantly opened,thereby helping to prevent" the possibilitybf' arcing.

"If a normally open design were desired,.i.e. having the contacts178'and 1'80open while the link assembly58 is in its lowermost positionandclosediwhen the link assembly 58 accelerates upwardly, itwould merelybe -necessary to (1) place the detent spring 108 below the trunnion link110, retained by a suitable'se at, (2) changethe position of the contactretainer cup 160 by rotatingit 180, and (3) reverse the position of thelever144 onthe knurled end 128 of the shaft 124.

The function of the novel toggle spring assembly 94 will now bedescribed. 50 long as normal operation of the engine prevails, the axesof both the toggle spring assembly 94 and the counter-balanced lever 80(see FIG. 3) will be positioned below the horizontal some predeterminedamount, say 5.8 degrees. The vector forces while the parts are in thisrelationship would be such that a downward force would prevail at thepoint of contact between the points of the right end cone 96 and thebottom of the conical wide-angle depression in the seat 86 at the end 88of the counter-balanced lever 80. The eifect could be likened to anegative rate spring, similar in function to a conventional snap-actionspring, requiring a particular force to actuate any movement thereof.Once this predetermined force is reached and upward movement of the cone96 and seat 86 begins, a progressively lower force would be required asthe angular relationship with horizontal decreases. It is in this mannerthat acceleration is produced once movement begins. The movement of thetoggle system 94 and the lever 80 continues until the yoke stop 66 abutsagainst the link stop screw 54, at

which time the angular relationship of the toggle spring 100 and lever80 axes with horizontal is approximately .5 degree, but still below thehorizontal.

It should be understood that the device 10 is designed such that so longas a low, normal engine operation decay rate of P occurs, the flow fromthe lower accumulator chamber 48 past the valve 198, into the valvechambers 194 and 188 and out through the conduit 192 to the upperchamber 50 would be such that the P --P differential (5 p.s.i., forexample) acting on the area of diaphragm 42 would provide a force lessthan the force required to initiate upward movement of the toggleassembly 94 and lever 80. However, in the event of an engine flameout, arapid P decay rate as high as 1500 p.s.i. per second could occur. Undersuch a circumstance, the flow from the accumulator chamber 48 to theupper chamber 50 through the passages just described would be too slow,and the P P differential across the diaphragm 42 would be sufficient toinitiate the upward movement of the, toggle assembly 94 and shaft 80.Then, as was described above, upward acceleration of the toggle assembly94 and shaft 80v would continue until the the-link 58'were to come intoc screw-'54;

It can now be seen that the link a have been travellingat arelativelyhigh s theprevio'usly described .040" compression: springl1ii8iseliminated, thereby causing the co an-d 1-80 to be snappedlquicklytapart by virtueof thv upward movement of the lever. 116. This, of 00reduces the possibility of arcing. w So long as thecontacts 178:and180'remain closed, there wouldbe a continuous' curent flow fror'rrthealternator of. the ignit'ion system 12 through the hermetically sealedconnectorswitch28 and back to the alternator. However, once'the contacts178 and 180 opemsuch aswould result from the upward movementof the linkassembly 56in the event of a fiameout as described above, the'currentflow from the alternator would thenIbe diverted to the igniter plugs oftheengine 14 for the reignitionthereof.

Attire same time that the ignitionis actuatedfollowing aiflameout,.thevalve. 198 closes againstthe seat 196, as was described above, and: thetimed ignition hold-in system becomes effective. This hold-in systemcomprises a series. of hold-injets 6'8 and? ayoke stop 66 inserted inthe axial-passage 70 in the link assembly 56. The operation of the timedignition hold-in system will. now be described:

While the yoke stop 66 is t abuttedtagainst the link stop screw 54; airflow will occur between the lower and upper chambers 48 and 50 by way ofthe transverse opening:72 in the link 58 and the holes174ithroughtheseries of hold-- in jets 68,.and thence through-the center of the yokestop 66 and out through the slotted opening '76 in the top of the yokestop 66 into the upper chamber 50. This greatly reduced air flow allowsP P to gradually decrease until such time as the P decay settles outafter which P gradually approaches P Regardless of the magnitude ofeither pressure, when P P is reduced below the critical value, thedownward component force in the toggle spring 100 and lever 80, whichare at rest some amount, say .5 degree, from horizontal, will be greaterthan the now decreased upward force on the diaphragm 42, and the togglesystem 94 and lever 80 will move downwardly. Movement of the lever 80about the pivot pin 84 will, in turn, move the link assembly 56downwardly toward the bottom stop 208, resulting in the closing of thecontacts 180 against the stationary contacts 178 and the opening ofvalve 198.

Hold-in time can be modified by changing the size of the openings 74 inthe hold-in jets 68, or by adjusting the r position of yoke stop 66.

In summary, it can be seen that the invention eliminates the need forcontinuous ignition, thereby lengthening ignition system life. Automaticoperation eliminates the need for pilot concern about reignition after aflameabout.

While applicants device forms the intended function in direct responseto a pressure difierential exceeding a critical value, it can also besaid that the device is responsive to the rate of change of a pressurebeing sensed. Thus, it can be seen that the invention, or somemodification thereof, may be employed wherever it is desired to sensethe rate of change of some pressure and to actuate some external deviceaccordingly. For example, it is possible that a valve or other systemcould be substituted for the switch 28.

While only one embodiment of the invention has been disclosed anddescribed, it is apparent that other modifications of the invention arepossible within the scope of the appended claims.

What we claim as our invention is:

1. A device for detecting flame-out in and energizing the ignitionsystem of a gas turbine engine having a burner chamber, said devicecomprising a body having a first chamber to which pressure indicative ofengine burner pressure is continuously communicated, a second chamber,

ieans ement except ,esulting a'id movetween said nt of saidpredetermined apid decrease in presing from an engine 'ng a burnerchamber sive to a decrease in d magnitude resultically operating saidignition system either mined time period or until said engine is reigm\t said time period.

3. In a gas turbine engine havni 1 burner chamber and an ignitionsystem, means responsive to a decrease in lbllI'HCl' chamber pressure ofthe rate and magnitude resulting from engine flameout for automaticallyoperating said ignition system and means for automatically renderingsaid ignition system inoperative when said engine is reignited.

4. In a gas turbine engine having a chamber in which the pressure dropsdrastically on engine flameout and an ignition system, means formaintaining said ignition system inoperative during normal engineoperation, means responsive to the pressure drop in said chamber of therate and magnitude occurring on flameout for automatically operatingsaid ignition system and means responsive to a subsequent increase inpressure in said chamber upon reignition of said engine for againautomatically ing from engin rendering and maintaining said ignitionsystem inoperative.

5. A device for detecting flameout in and energizing the ignition systemof a gas turbine engine, said device comprising a body having a firstchamber to which engine operating pressure is continuously communicated,a second chamber, a common movable wall between said chambers, meansassociated with said movable wall for preventing the movement of saidmovable wall toward said first chamber except upon a decrease inpressure in said first chamber resulting in a predeterming pressuredifferential across said movable Wall, and a restricted communicationbetween said chambers preventing the attainment of said predeterminedpressure differential except upon a rapid decrease in pressure in saidfirst chamber resulting from an engine fiameout.

6. In a gas turbine engine having an ignition system, means responsiveto a decrease in engine operating pressure of the rate and magnituderesulting from engine fiameout for automatically operating said ignitionsystem either for a predetermined time period or until said engine isre-ignited within said time period.

References Cited by the Examiner UNITED STATES PATENTS 2,959,007 11/1960Gregory et al. -39.82

FOREIGN PATENTS 660,178 10/1948 Great Britain.

MARK NEWMAN, Primary Examiner.

SAMUEL LEVINE, Examiner.

1. A DEVICE FOR DETECTING FLAME-OUT IN AND ENERGIZING THE IGNITION OF AGAS TURBINE ENGINE HAVING A FIRST CHAMBER, SAID DEVICE COMPRISING A BODYHAVING A FIRST CHAMBER TO WHICH PRESSURE INDICATIVE OF ENGINE BURNERPRESSURE IS CONTINUOUSLY COMMUNICATED, A SECOND CHAMBER A COMMON MOVABLEWALL BETWEEN SAID CHAMBERS, MEANS POSITIONED IN SAID SECOND CHAMBERRESISTING THE MOVEMENT OF SAID MOVABLE WALL TOWARD SAID FIRST CHAMBEREXCEPT UPON A DECREASE IN PRESSURE IN SAID FIRST CHAMBER RESULTING IN APREDETEMINED PRESSURE DIFFERENTIAL ACROSS SAID MOVABLE WALL, AND ARESTRICTED COMMUNICATION BETWEEN SAID CHAMBERS PREVENTING THE ATTAINMENTOF SAID PREDETERMINED PRESSURE DIFFERENTIAL EXCEPT UPON A RAPID DECREASEIN PRESSURE IN SAID FIRST CHAMBER RESULTING FROM AN ENGINE FLAME-OUT.